Flame-proof switch mechanism



Oct. 15, 1929.

C. B. COATES FLAMEPROOF SWITCH MECHANISM Filed May 1925 2 Sheets-Sheet 2 ARMATURE CABLE CONNECTION MAIN SWITCH REVERSING swn'cn INVENTOR [fiat/es 5. foa/fes Patented Oct. 15, 1929 ."umrsn isra'rss PATENT OFFICE CHARLES COATEQOI CLEVELAND, OHIO, ASSIGNOR T CHICAGO PNEUMATIC TOOL COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY FLAME-PROOF SWITCH MECHANISM Application filed May 5, 1925. Serial No. 28,102.

This invention relates to switch mechanism for use in gaseous or dust laden atmospheres wherev there is danger that an open spark might produce an explosion. While certain features of the invention are capable of general application, the invention is particularly directed to quick acting switches having a reciprocatory bar arranged to move independently of the controlling member, such as are commonly used on portable elec'trical tools.

Among the objects of the invention are to provide a switch device of the type described so constructed and arranged that any sparking or arcing, or even an explosion within the switch casing, is effectively prevented from communication with the surrounding atmosphere, to hinder or to prevent tampering with the flame proof features of the switch mechanism, to seal the feed cable end in place and against thepossibility of flame working therealong, to provide a main switch casing arranged for the convenient insertion or removal of a reversing switch, to provide a unit reversing switch structure to fit said main switch casing, and in general to improve prior devices of this character in the interests of safe and eflicient operation. In order to illustrate the invention a preferred embodiment thereof is shown in the accompanying drawings, in which:

F ig. 1 is a longitudinal sectional view of a device in accordance with the present invention containing a main switch only;

Fig. 2 is a fragmentary horizontal sectional view substantially on the line 22 of Fig. 1;

Fig. 3 is a wiring diagram for the switch shown in Fig. 1;

Fig. 4 is a view similar to Fig. 1 but showing the device provided with a reversing switch in addition to the main switch;

Fig. 5 is a plan view of the under or switch side of the unit reversing switch structure shown in Fig. 4; and

Fig. 6 is a wiring diagram for the device shown in Fig. 4.

The embodiment of the invention chosen for the purpose of illustration comprises a casing 7 arran ed to be secured in any suitable or known manner to the electrical machine to be controlled thereby, such as an electric drill A shown in a fragmentary manner partly in elevation and partly in section in Figs. 1 and 4. Casing 7 contains therewithin a chamber 8 for the main switch, a chamber 9 for the cable connection and fuses, and is formed with outwardly extending walls 7 defining a recess 10 of substantial size adjacent the main switch chamber 8 for additlonal switch mechanism if desired. When chamber 10 is not used to house switching mechanism, as when used on a non-reversible motor, recess 10 is sealed by a tight fitting cover plate 11 secured by a suflicient number of screw bolts 12 which may be locked in any suitable manner as by a wire 13 to maintain the seal. I

The particular form of main switch shown in the present instance as disposed in chamber 8 consists of spaced pairs of contacts 14 and 15 arranged to be respectively bridged by movable contacts 16 and 17 mounted upon, but insulated from, a plate 18 which extends through an opening in the walls of chamber 8 and is fastened to a head 19 arranged for reciprocating movement in a handle extension 20 of the switch casing, which casing may be an Integral part thereof or may be in the form of a separate member. As shown it is a separate member which is welded to or otherwise permanently secured upon the casing. Head 19 has a projecting stem 19 secured to a guide member 19 disposed in spaced relation to head 19 within the handle 20. The reciprocating movement of the head 19 for closing and opening the main switch is effected by a well known form of quick acting mechanism in the form of a bar 21 loosely connected to the guide member 19 by a pin 21 extending through a slot 19. Bar 21 has locking slots 21 and 21 which cooperate with fixed stops 22 and 23 in a well known manner, the throw of bar 21 being effected by a trigger member 24 connected to the bar 21 by a coiled spring 25 and having project-ions or shoulders 24 and 24 to engage bar 21 and force it out of locking engagement with respective stops 22 and 23 immediately prior to its movement under the impulse of spring 25. Trigger 24 is maintained in its on or off position by a coiled spring 26 which in accordance with the usual practice tends to throw the switch to off position on a slight movement of the trigger from the on position.

Since one of the principal objects of the present invention is to prevent sparks or flame which may be produced within the switch casin g from reaching the surrounding atmosphere adequate means are provided for this purpose in the handle in which the control mechanism for the main switch is mounted. A preferred means takes the form of a fixed barrier sleeve 27 within the hollow handle 20 adjacent the casing 7 and secured thereto as by screws 28. Sleeve 27 provides a long tight fitting bearing for rod 19 so that any flash or flame from the main switch is efiectively quenched at this point. To insure this sleeve against accidental or intentional removal an annulus 29 is sleeved over handle 20 with a press fit and entirely conceals the fastening screws 28.

Referring now to the cable connection into chamber 9 in which safety fuses 30 are mounted, the cable plug 31 is of substantial length and extends well into its socket with a tight fit and supports a spring pressed contact block 32 of insulating material to which the leads of the cable 33 are secured. Any desired or suitable positive anchorage for the cable may be utilized such as block 34 secured toplug 31 and projecting through a slot 31 in the wall thereof into a recess 33 in the cable insulation. The sealing of the cable against escape of flame therealong from the blowing of fuses 30 is accomplished by providing a recess 31 in the plug adjacent the end of cable 33 and in filling this recess after the cable end is in place with semi-plastic material 35, preferably having an asphaltum base, which will not deteriorate or work loose from the walls of the recess or from the cable.

It will now be evident that the electric switch device disclosed in Fig. 1 has effective means sealing all openings against the escape of sparks and flame which might result from the operation of the main switch or from an explosion within the switch casing, these means taking the form of the cover for recess 10, the barrier block or sleeve 27, and the fixed anchorage and seal for the entering cable 33.

Referring now to Figs. 4, 5 and 6 attention will be directed particularly to the utilization of 'recess 10 for the mounting of additional switch mechanism, and to the particular type of switch mechanism developed for convenient insertion therein without impairing the frame proof properties of the switch mechanism previously discussed, which have all been retained as is evident from an inspection of Fig. 4. To adapt the switch structure of Fig. 1 to the use of additional switch mechanism a plate 11 (Figs. 4 and 5) is provided which is interchangeable with cover plate 11 (Fig. 1). Upon plate 11 is mounted the entire additional switch mechanism so that the same is inserted within chamber 10 as a unit by the mere substitution of plate 11 for plate 40 and 41 (Figs. 5 and 6). The plate 11 also has a boss 42 of substantial length extending transversely thereof-from its underside and formed with a bore serving as a tight fitting bearing for a transversely mounted shaft 43 beyond boss 42 on both sides of projecting the plate. hence on opposite sides of plate 11',

Shaft 43 carries at itsends, and

substantially parallel members or arms-43 and 43.

Arm 43 supports an insulating plate 44 carrying the movable contacts orbrushes 45 and I 46 which cooperate with the terminals 39, 40

and 41. Arm 43 may be integral with shaft 43 if desired and arm 43 which serves as an operating handle for the switch mechanism may be keyed to the opposite reduced end of shaft 43 and secured thereto by suitable means such as a nut 47 Thus'movement of the operating handle 43 between suitable stops 48 on the top of plate 11 will operate the switch disposed upon the underside of plate 11*.

Since the switch in chamber 8 is ordinarily the main switch and that in chamber 10v the reversing switch and since operation of the reversing switch when the main switch is on is likely to result in damage to the motor it is desirable to provide means under control of the main switch when in on position for locking the reversing switch. A preferred means for this purpose comprises a slide 49 adjacent the outer end of arm 43 arranged to be forced upwardly by an inclined cam surface 50 on head '19 to project a stop 49 into the path of movement of arm 43, when the operating member of the main switch is moved to the closed position. Slide 49 is moved back to inoperative position when the main switch is thrown to the off position by a spring pressed plunger 51 which engages the same, this plunger being mounted in a guide sleeve 52 which fits an opening 53 in a projection 7 b of the walls 7 a of recess 10 and is retained in place by plate 11 as indicated. The coiled spring 54 for actuating plunger 51 abuts against plate 11. When plate 11 is used to cover recess 10, a plug 55 which may be separate from, attached to, or integral with, plate 11 may be utilized if desired to fill opening 53.

From the above it will be apparent that the present invention providesa gas tight and explosion proof switch device for use on electric'al machines in gaseous and dust laden atmospheres, that all possible avenues of escape nism to conform to the type of motor is accomplished with a minimum of trouble and expense and without actual structural modification of the device due to the provision of interchangeable covers for a recess in the device and the mounting of the reversing switch structure as a unit on one of the covers.

While what is now considered to be the preferred form of the invention has been herein shown and described, it is to be understood that the invention is not limited to the specific form shown but covers all changes, adaptations and modifications within the scope of the appended claims.

I claim as my invention:

1. The combination with a. portable electric tool of an electric control device therefore comprising a casing. switch mechanism therein, a grip handle extending from said casing, a reciprocatory operating member for said mechanism within said handle, and means tightly fitting said member and preventing the escape of sparks or flame from said casing along said member.

2. The combination with a portable electric tool of an electric control device therefor comprising a casing, switch mechanism therein, a grip handle extending from said casing, a reciprocatory rod for operating said mechanism extending into said handle, and a fixed sleeve tightly fitting said rod for preventing the escape of sparks or flame from said casing along said rod- 3. In an electric control device, a casing, switch mechanism therein, a grip handle extending from said casing, a reciprocatory rod for operating said mechanism extending into said handle, and a sleeve secured within said handle having a bore of substantial length receiving said rod with a tight sliding fit for preventing the escape of sparks or flame from said casing along said rod.

4. The combination with a portable electric tool of an electric control device therefor comprising a casing, switch mechanism therein, a grip handle extending from said casing, a reciprocatory rod for operating said mechanism extending into said handle, a sleeve in said handle tightly fitting said rod, means fixedly securing said sleeve in place, and means preventing the removal of said securing means.

'5. In an electric control device, a casing, switch mechanism therein, a handle extending from said casing, a rod for operating said mechanism extending into said handle, a sleeve in said handle tightly fitting said rod, means securing said sleeve in place, and an annulus engaging said handle with a press fit to prevent the removal of said securing means.

6. In an electric control device, switch mechanism therewithin, member for said mechanism yond said casing,

a casing, a control extending hemeans cooperating with said control member to prevent the escape of sparks or flame therealong, said casing being formed with a recess for additional switch mechanism and adapted to be closed by interchangeable co'ver plates for sealing said recess, one of which plates may carry said additional switch mechanism.

7 A manual support and control handle for a portable electric tool comprising :1 casing, switch mechanism therewithin, means for operating said switch mechanism, said casing being formed with a recess for additional switch mechanism, said recess being in free communication with the remainder of the casing, and a removable cover plate for said recess.

8. A manual support and control handle for a portable electric tool comprising a casing, switch mechanism therewithin, means for operating said switch mechanism, said casing being formed with a recess for additional switch mechanism, a plain cover plate for closing said recess, and a second cover plate interchangeable with said plain cover plate and carrying said additional switch mechanism.

9. In an electric control device, a casing, switch mechanism therewithin, means for operating said switch mechanism, said casing being formed with a recess for additional switch mechanism, and a detachable cover plate for said recess carrying dependent from its lower face said additional switch mechanism and upon its upper face actuating means therefor.

10. In an electric control device, a casing, a main switch therewithin, means for operating said switch, said casing being formed with projecting walls defining a recess, and a detachable cover plate for said recess carrying dependent from its lower face reversing switch mechanism, and an operating shaft for said mechanism projecting through said plate.

11. In anelectric control device, a casing, a main switch therewithin, means for operating said switch, said casing being formed with projecting walls defining a recess, a remov able cover plate for said recess supporting reversing switch mechanism therein, and a shaft projecting through said plate and provided with a handle for operating said mechanism.

12. In an electric control device, a casing, a main switch therewithin, means for operating said switch, said casing being formed with projecting walls defining a recess, and a removable cover plate for said recess carrying reversing switch mechanism including terminals supported from the underside of said plate within said recess, and wiping contacts for said terminals operated from the upper side of said plate.

13. In an electric control device, a casing, a main switch therewithin, means for operating reversing switch mechanism including terminals supported from the underside of said plate within said recess, and a transverse shaft extending through said plate and supporting beneath its lower face wiping contacts for said terminals and above its upper face an operating handle therefor.

14:. In an electric control device, a casing, a main switch therewithin, means for operating said switch, said casing being formed with projecting walls defining a recess, and a cover plate for said recess carrying reversing switch mechanism including terminals supported from the underside of said plate within said recess, a transverse shaft extending through said plate and supporting substantially parallel arms above and below said plate, one of said arms serving as an operating handle and the other as a support for the wiping contacts for said terminals.

15. In an electric control device, a casing, a main switch therewithin, means for operating said switch, said casing being formed with projectingwalls defining a recess, a removable cover plate for said recess, said plate having a boss providing a' long bearing for a transversely mounted shaft extending above and below said plate, and reversing switch. mechanism on the underface of said plate within said recess controlled by said shaft.

16. In an electric control device, a casing, switch mechanism therewithin, a control member for said'mechanism extendingbeyond said casing, means cooperating with said control member to prevent the escape of sparks or flame therealong, said casing being formed with a recess for additional switch mechanism, a removable cover plate for said recess having an operating shaft for said additional switch mechanism extending therethrough, said plate providing a long close fitting bearing for said shaft to prevent the escape of sparks and flame.

17. In an electrical control device, a casing, switch mechanism therewithin, a control member for said mechanism extending be yond said casing, means cooperating with said control member to prevent the escape of sparks or flame therealong, said casing being formed with a recess for additional switch mechanism, a removable cover plate for said recess supporting upon its under face said additional switch mechanism, an operating shaft for said last named switch mechanism, and a handle on said shaft above the upper face of said plate, said plate providing a long close fitting bearing for. said shaft to prevent the escape of sparks and flame.

18. In an electric control device, a casing, a main switch therein, an operating member for said switch, said casing being formed with a recess having reversing switch mechanism therewithin, a cover plate for said recess, and

locking mechanism for said reversing switch maintained in place by said cover plate and operated when said main switch is on.

19. In an electrlc control device, a casmg, a mam switch therewithln, means for.operating said switch, said casing being formed with projecting walls defining a recess, a

cover plate for said recess carrying dependent i from Its lower face reversing switch mechanism, an operating shaft for sald mechanlsm projecting through said plate, and locking a main switch therewithin, means for operat' ing said switch, said casing being formed with projecting walls defining a recess, a cover plate for said recess carrying reversing switch mechanism including terminals supported from the under side of'said plate within said recess, a transverse shaft extending through said plate and supporting substantially parallel arms above and below said plate, one of said arms serving as an operating handle and the other as a support for the wiping contacts for said terminals, and locking means arranged to engage one of said arms'when the main switch is on, said locking means being maintained in operative position by said cover plate.

21. In an electric control device, a casing, a main switch therein, a control member for said main switch, said casing being formed with projecting walls defining a recess, a cover platefor said recess carrying reversing switch mechanism including terminals supported from the under side thereof within said recess, a transverse shaft extending through said plate and supporting substantially parallel arms above and below said plate, the upper arm serving as an operating handle and the lower arm as a support for wiping contacts for said terminals, and locking mechanism for said reversing switch including a.

stop forced into the path of movement of said lower arm when the main switch is on, said locking means being maintained in place by said cover plate and being controlled by said main switch control member.

22. A control device for portable electric tools comprising a casing, switch mechanism therein, a grip handleextending from said casing, a rod for operating said mechanism projecting within said handle, means on said handle for actuating said rod with a snap action, and means within said handle closely fitting said rod for preventing the escape of sparks or flame along said rod.

23. A unit switch device for mounting in a recess on the machine to be controlled thereby comprising a plate arranged to form a cover for the recess, switch mechanism including fixed contacts mounted upon one side of said plate to extend into the recess, and operating means for said mechanism having an elongate bearing in said plate for confining and quenching any flame originating in said recess.

24. A unit switch device for mounting on a machine to be controlled thereby comprising a plate arranged to serve as a cover for a recess in said machine and providing an elongate transverse bearing, switch mechanism supported on the under side of said plate to extend into the recess including terminals and one or more wiping contacts for said terminals operated from the upper side of said plate, and means journaled in said plate bearing providing an operating member above said plate and a support for said wiping contacts beneath said terminals.

25. A unit switch device for mounting on a machine to be controlled thereby comprising a plate arranged to serve as a cover for a recess in said machine, terminals supported from the under side of said plate to extend within the recess, said plate having a perforated boss providing a bearing of substantial length, a transverse shaft journaled in said perforated boss, at least one contact for said terminals carried by said shaft, and means on said shaft above said plate for moving said contact across said terminals.

26. A unit switch device for mounting on a machine to be controlled thereby comprising a plate arranged to serve as a cover for a recess in said machine, terminals supported from the underside of said plate to extend within the recess, a transverse shaft extending through said plate and supporting substantially parallel arms above and below said plate, one of said arms servin as an operating handle, the other arm being disposed beneath said terminals and having upwardly directed wiping contacts for said terminals.

CHARLES B. COATES. 

